2.1. MONOCLONAL ANTIBODIES
Kohler and Milstein are generally credited with having devised the technique that successfully resulted in the formation of the first monoclonal antibody-producing hybridomas [G. Kohler and C. Milstein, Nature 256: 495-497 (1975); Eur. J. Immunol. 6: 511-519 (1976)]. By fusing antibody-forming cells (spleen lymphocytes) with myeloma cells (malignant cells of bone marrow primary tumors) they created a hybrid cell line, arising from a single fused cell hybrid (called a hybridoma or clone) which had inherited certin characteristics of both the lymphocytes and myeloma cell lines. Like the lymphocytes (taken from animals primed with sheep red blood cells as antigen), the hybridomas secreted a single type of immunoglobulin specific to the antigen; moreover, like the myeloma cells, the hybrid cells had the potential for indefinite cell division. The combination of these two features offered distinct advantages over conventional antisera. Whereas antisera derived from vaccinated animals are variable mixtures of polyclonal antibodies which never can be reproduced identically, monoclonal antibodies are highly specific immunoglobulins of a single type. The single type of immunoglobulin secreted by a hybridoma is specific to one and only one antigenic determinant on the antigen, a complex molecule having a multiplicity of antigenic determinants. For instance, if the antigen is a protein, an antigenic determinant may be one of the many peptide sequences [generally 6-7 amino acids in length (M. Z. Atassi, Molec, Cell. Biochem. 32: 21-43 (1980)] within the entire protein molecule. Hence, monoclonal antibodies raised against a single antigen may be distinct from each other depending on the determinant that induced their formation; but for any given clone, all of the antibodies it produces are identical. Furthermore, the hybridoma cell line can be reproduced indefinitely, is easily propagated in vitro or in vivo, and yields monoclonal antibodies in extremely high concentration.
Monoclonal methods are generally applicable and have been used to produce antibodies to antigens other than the sheep red blood cells used by Kohler and Milstein. For instance, it has been reported that monoclonal antibodies have been raised against tumor cells [U.S. Pat. No. 4,172,124] and viruses [U.S. Pat. No. 4,196,265]. The production of monoclonal antibodies against certain collagens, procollagens (natural precursors of collagens) and a collagen-associated glycoprotein has also been reported. Linsenmayer et al. reported using the cell hybridization technique to produce monoclonal antibodies against chick Type I collagen [Proc. Natl. Acad. Sci. U.S.A. 76(8): 3703-3707 (1979)]; Linsenmayer and Hendrix later reported having produced a monoclonal antibody specific for chick Type II collagen [Biochem. Biophys. Res. Commun. 92: 440-446 (1980)]. Both antibodies have been used for biochemical and cytological studies of extracellular matrices involved in the morphogenesis of the embryonic chick. Walsh et al. [Dev. Biol. 84: 121-132 (1981)] have reported producing a monoclonal antibody against human fibronectin, a collagen-associated glycoprotein, as part of an investigation to define human muscle surface antigens. The biochemical and immunological characterization of monoclonal antibodies specific for human collagens, Types I, III and IV, and human procollagens Types I and III has recently been reported [N. SundarRaj et al., J. Cell Biol. (Abstr.) 91(2): 8027 (1981)]. Finally, a monoclonal antibody against the collagen degrading enzyme elastase has been used to study the pathogenesis of inflammatory joint disease [S. Gay et al., VIIIth Southeastern Meeting, Amer. Rheum. Assoc., Abstr. 1, (1981)].